Preheat oven to 350°F and line a 9x13 baking dish with parchment paper and lightly grease the sides.
To make the brownies, in a large mixing bowl whisk together the melted butter and cocoa powder until smooth.
Add the sugar and mix until well combined.
Add the eggs and vanilla extract and whisk until fully incorporated and smooth.
Stir in the flour just until combined.
Spread batter evenly into baking dish. Bake for 20-25 minutes and until the edges are just starting to pull away from the sides and the middle is no longer glossy looking.
Let brownies cool for 15-20 minutes and start the peanut butter filling.
In a stand mixer or with hand beaters, beat together the melted butter, peanut butter, vanilla, and powdered sugar until everything is evenly combined.
Drop dollops of peanut butter filling on top of the brownies. Spread it out evenly with your fingertips or off set spatula to cover all the brownies.
In a microwave safe bowl, melt the chocolate chips and cream together for 30 seconds, stir. Melt in 10 second intervals after that if needed.
Spread the chocolate over the peanut butter filling evenly. Work quickly, the ganache will set fast.
Chill in refrigerator for at least one hour before serving.
Slice and serve!